PIP and open-angle glaucoma: Interestingly, a subgroup of 12 upregulated proteins in naïve POAG patients was found to be downregulated in the medically controlled POAG groups treated with prostaglandin analogs, i.e., LCN1, LYZ, lactotransferrin (LTF), proline-rich protein 4 (PRR4), prolactin-inducible protein (PIP), AZGP1, polymeric immunoglobulin receptor (PIGR), CST4, IGKC, Ig alpha-2 chain C region (IGHA2), immunoglobulin J chain (IGJ), and Ig alpha-1 chain C region (IGHA1).